Other than the temperature at which it is served, the most likely cause of beer tasting differently is where it is manufactured. The water used may affect the flavour, as may slight variations in the brewing process (this could also apply from batch to batch in the same brewery). This is less likely to affect mass-produced beers which mostly taste of chemicals anyway. I imagine that the Orval you had is brewed under licence in the US, so will taste different to that drunk in Belgium. Even imported beer can taste different; in the UK Becks make a selling point of their beer not being brewed under licence, but it still doesn't taste the same as in Germany - must be the travelling.