All of the countries in the EU are Allies in one fashion or the other. Some are allied in a stronger fashion on some issues and less strongly on others. But regardless, the ties between the EU and the US are strong . . . we have each others back on many issues.
EDIT: Inserting PotUS in the original question is also a bit off . . . the EU would be allied with the US regardless of the figure sitting in the White House.
[Edited 2006-06-24 02:34:35]
FOR THOSE THAT FOUGHT FOR IT, FREEDOM HAS A FLAVOR THE PROTECTED WILL NEVER KNOW OR UNDERSTAND
In Europe I think it goes without saying that the UK is our best and closest ally. Sure our countries got off to a rocky start with each other and the little flair up both sides had in 1812, but both countries have supported each other well.
Australia is a good ally of ours as well as pointed out earlier. They have soldiers in Iraq as well, sent men to Vietnam and the ANZAC forces have been involved in both world wars.
Do you mean at political/governmental level, and/or amongst the populace?
For both, I'd say Poland, because, like it or not, there is an increasingly yawning gap between the two in the UK.
Since 2003 funnily enough.
But that may recover with a change in the White House occupant.