I'm also travelling to the US in April. My passport was due to expire in June but i was told i needed at least 6 full months on it to travel to the US so i've had to renew it. Phone the passport office and check if you want to be doubly sure. They add the remaining months onto your new passport anyway, so for example, you new one will last for 10 years and 8 months (if you renewed it this month).