What is the Lithuanian equivalent of $10 American, in terms of purchasing power?

Well petrol is around ~$6.00 per US gallon in Lithuania, which is cheap compared the UK, which would be $7.70 per US gallon.

But comparing petrol prices is not useful because the USA has incredibly cheap petrol in general.

Maybe looking at the beer price will give you a little more insight? about $1.50—$2.00 for 0.5L (about 19 fl. oz.) in the bars. (plus they have very good and very strong beer)

Maybe property prices are the most telling, though? A quick internet search shows us we can get a 4 bedroom apartment in the centre of Kaunas (the second city) for a tasty $475/mo!

Considering a 4 bed house in Sheffield (cheap!) costs around $1,900/mo that’s pretty nice…

Just for interest, btw, here is a (very) basic 4 bed apartment in London, relatively cheap area, $3,280/mo

According to the IMF, Lithuania’s GDP in 2010, based on current prices, was U.S. $35.2 billion. In PPP, it was U.S. $54.6 billion. Therefore, U.S. $10 are equivalent to U.S. $15.54 in Lithuania.

Your request requires two “degrees” of conversion.

Namely, what is the conversion rate of USD into Lithuanian Litas? ($1 = 2.52 LTL)

Secondly, what can 25.20 LTL buy in Lithuania? That I can’t tell you. As @The_Idler correctly notes, people do things differently in different places. A Lithuanian (or most other European) wanting to travel between cities would be much more likely to take a train than to drive.