“MY fellow Americans,” the letter begins, Star-Spangled Banner fluttering in the background. “Like baseball, apple pie and ice cold beer (wrapped in a red, white and blue label), Anheuser-Busch is an American original.” Now, the letter continues, hostile forces are threatening “our city, our nation and our workers”. Readers are urged to “fight the foreign invasion” and take that fight to “the internet, the streets, the marble halls of our capitals”.

By last night more than 27,000 had heeded the call, signing an online petition to stop the takeover of the brewer of Budweiser. Only days after launching its $46 billion (£23 billion) unsolicited bid for Anheuser, Belgian/Brazilian rival Inbev is facing its first big obstacle: American politics in an election year.

Politicians in St Louis, Missouri, Anheuser’s home town, have already come out against the deal. Governor Matt Blunt said he was strongly opposed to the sale and found the offer “deeply troubling”.

The SaveAB.com website was launched by Blunt’s former chief of staff, Ed Martin. “Shareholders should resist choosing dollars over American jobs,” Martin said. “Selling out to the Belgians is not worth it because this is about more than beer: it’s about our jobs and our nation.” Harry Schumacher, publisher of Beer Business Daily, said: “This will get a lot of play. I even imagine the two presidential candidates will come in on it.”

Budweiser is a national icon, as well as the employer of more than 30,000 people, including 6,000 in St Louis. The forces of globalisation, a weak dollar and rocky financial markets have led to a sharp rise in foreign ownership in America of everything from companies to landmark buildings. The cable news channel CNN has been running the Budweiser story under the headline America For Sale.

The bid for Bud is uniting critics across the political spectrum. As well as St Louis’s Republican governor, officials at the Teamsters union, which represents 1.4m Americans including 7,500 Anheuser workers, have said they want the brewer to remain American.

The Teamsters recently gave their support to Democratic presidential nominee Barack Obama. It remains to be seen whether Obama or his Republican opponent John McCain will get involved. McCain’s position is complicated by the fact that his wife Cindy is chairman of Hensley, third-largest distributor of Anheuser-Busch products. “Anything he says could look self-interested,” said Schumacher. But the political pressure for the candidates to say something is unlikely to abate.

Before the bid became official the Busch family, scions of company founder Adolphus Busch, had made it clear that they opposed a takeover. August Busch IV, chief executive, told beer distributors in April that the company started by his great-great-grandfather would not be taken over “on my watch”.

The Busches control a fraction of Anheuser’s shares but are politically well-connected. August Busch III, former company chief and father of the current boss, has been a regular contributor to McCain’s political funds. His son has backed the Democrats.

Inbev’s chief executive, Carlos Brito, has already moved to defuse some of the political heat. He has pledged to keep Anheuser’s American headquarters in St Louis and made reassuring noises about jobs. In a conference call last week with investment analysts, Brito said Inbev wanted to extend Budweiser’s reach, not diminish it.

Part of the company’s rationale for the acquisition was to strengthen Bud’s brand, he said.

“Budweiser would be a flagship brand. It’s a brand known by a lot of consumers around the world. They look for international premium brands.”

Brito said the plans do not foresee the closure of any breweries in America and that the company’s name will reflect the Anheuser and Budweiser heritage.

Inbev was formed in 2004 when Belgium’s Interbrew merged with South America’s biggest brewer Ambev. Company insiders said there was no emotional attachment to the Inbev name.

“Inbev has a lot of bridge-building to do,” said Benj Steinman, editor of the Beer Marketer’s Insights trade publication. He said the Busch family were likely to play “every angle they can” to see off Inbev.

But for all the noise the bid is generating, there seems to be little to support genuine grounds for political objection. Inbev has a small share of the American beer market, so competition issues are unlikely to block a deal.

The last time a foreign bid for an American company was scuppered after a political outcry was Dubai Ports World’s 2006 bid for the management contracts for six North American ports. But beer is not a national-security issue.

“In the end, we have a free market system,” said Schumacher. “It’s a hot political potato now but I doubt anything can be done to stop it.”

Anheuser’s directors have said they will evaluate the proposal carefully. “The board will pursue the course of action that is in the best interests of Anheuser-Busch’s stockholders,” the company said.

There has been some speculation that Anheuser might try to buy the 50% of Mexican brewer Grupo Modelo, maker of Corona, that it does not own.

Such a move might make Anheuser too expensive for Inbev. But with shareholders already being offered a substantial premium by Inbev, such a move could invite legal action.

For all of Inbev’s assurances to the contrary, its critics may be right to worry about job cuts at Anheuser-Busch. The American company has a reputation for free spending, especially on marketing; Inbev has a reputation for penny pinching.

Because of its size – Anheuser controls nearly half the beer market in America – Anheuser-Busch may be a ripe target for cost-cutting and Inbev will have tens of billions of reasons to do it. The company plans to pay for the deal with $40 billion in debt, a huge sum in a market where banks have tightened their standards after a global credit crunch.

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