The Democrats lost because of disappointment with the current administration. Voters believed that US President Barack Obama had failed to deliver on his promises. His landmark healthcare reform legislation has already been signed into law but it could be tweaked by the Republicans.
In addition, there was anger among voters who believed there was too much government intervention.
The main reason for the shift was domestic, not foreign. Americans tend to adopt a bipartisan approach to foreign affairs, while remaining divided on domestic issues. Following their election victory, the Republicans may demand greater defence spending.
They are traditionally concerned more about defence initiatives. This means there could be more American involvement in the global arena.
The Republicans are conservative and they support a strong America. The US has significant overseas commitments. It is likely that Republicans will get tougher with countries such as North Korea, Afghanistan and Iraq.
The mid-term election was fought almost entirely on domestic issues rather than foreign policy. Therefore, it remains to be seen what approach the Republicans will take on foreign affairs.
There could be a heated debate on China, America's largest trading partner and budding economic superpower.
American lawmakers have always complained that Beijing artificially undervalues its currency to boost its exports, leading to job losses in the US.
Now that the Republican Party has come back strongly after losing the presidential election, there is a possibility it will seize the chance to protect American interests at the expense of ruffling a few feathers.