8.3.7.1.3. In-flight fuel management
(EU-OPS 1.375(b))
The flight must be conducted so that the expected usable fuel remaining on arrival at the destination aerodrome is not less than:
(a) the required alternate fuel plus final reserve fuel, or
(b) the final reserve fuel if no alternate aerodrome is required.
However, if, as a result of an in-flight fuel check, the expected usable fuel remaining on arrival at the destination aerodrome is less than:
(a) the required alternate fuel plus final reserve fuel, the commander must take into account the traffic and the operational conditions prevailing at the destination aerodrome, at the destination alternate aerodrome and at any other adequate aerodrome, in deciding whether to proceed to the destination aerodrome or to divert so as to perform a safe landing with not less than final reserve fuel;
(b) the final reserve fuel if no alternate aerodrome is required, the commander must take appropriate action and proceed to an adequate aerodrome so as to perform a safe landing with not less than final reserve fuel.
The commander shall declare an emergency when calculated usable fuel on landing, at the nearest adequate aerodrome
The very same rule is applicable when you go to the US.