@Cow:
Can USA take Denmark during combat and cross the canal during non combat on the same turn? I know UK can cross it as soon as his turn comes.
No. Page 9 of the rule book says:
If your side (but not necessarily your power) controlled a canal or narrow strait at the start of your turn, you may move sea units through it (you can’t use it in the same turn that you capture it).
If the USA took Denmark during combat, it was Axis-controlled at the start of the USA’s turn, so it can’t be crossed during non-combat.