No. The Euro software version starts with V220 (up to sw 0170) or V221 (beginning with 0330), the US software version starts with V222. The RNS-E will not accept a software update from the other region, even though the SOFIDX is higher.
What you can do is to modify a couple lines in LOADING.KWI to make the US software look like a Euro update. Together with a modified INDEX.TXT the RNS-E will accept the update. and If done correctly, future updates will be automatic (at least if the SOFIDX on the RNS-E is lower than the SOFIDX on the udpate CD).