My patrilineage is very easy to trace since they were middle nobility in England until they got caught up in the Gunpowder Plot (it was hatched at the family castle, no joke!) & were banished to the US. Once they got to America they're a little harder to trace but the surname is very, very rare so it's not impossible (like, say, Johnson or Smith would be). I went to 'my' family's castle in 2000 & the whole tree is there, right back to 1066.
I traced my dad's mom's family back to about 1600; they emigrated to the US in the early 20th Century from Germany, and a very helpful record keeper in Bavaria helped me from I think 1621 (?) til they left for the States.
My mom's mom's family is again fairly easy because they became minor nobility in England in the late 1400s & got sent here in the middle of the 18th Century, and their surname is relatively uncommon.
My mom's dad's family is nearly impossible since they are Scandinavian, and the damn last name changes every generation. I've only been able to trace them back to the early 1800s, when my great great whatever grandfather emigrated to the US.
Public records in the US are usually pretty good; you should be able to trace your ancestors from when they got here til now with public info - if you're willing to follow the trail, since you often have to physically visit the library or records hall where they are. Records in Germany are phenomenal, if you have German ancestors. I had good luck with written & then email correspondence with a record keeper there. Dunno 'bout other countries.