Can someone explain how this massive sentence works


> アメリカやヨーロッパなど6つの国は、イランが核兵器をつくろうとしているのではないかと考えて、経済制裁（＝貿易などを禁止すること）を続けていました。

America and Europe etc plus 6 countries (this is the topic)  
Iran is trying to make nuclear weapons  
Since it is not prohibited economic sanctions (the thing that prohibits
international trade) are continuing.

I get the basic gist but I don't really understand lots of the grammar.

Especially:

  * What is it really saying about America? It seems the topic of individual clauses changes lots
  * I understand the つくろうとしている。But not the のではないかとかんがえて。 Does it mean since it is not prohibited? I don't understand how the grammar works here. ～ので？ ～かと？

Cheers




To break down:

  * The main topic remains the same throughout the sentence: アメリカやヨーロッパなど6つの国 (lit. "six countries including America and Europe"). As I said elsewhere, this phrase seems a bit odd, but I think the author wanted to say "America and _five_ European countries".
  * And those 6つの国 serves as the subject of the following two verbs: 考えて and 続けていました。 So the basic structure of the sentence is 「6つの国は、～と考えて、～を続けてきました。」("The six countries _thought_ [something], and _have continued_ [something]").
  * ～と考える is "think ～", and と here is the quotative particle. イランが核兵器をつくろうとしているのではないか is what と refers to, so this is what the six countries thought. I think you failed to catch this part.
  * In 「イランが核兵器をつくろうとしているのではないか」, 
    * You're understanding of イランが核兵器をつくろうとしている is perfect.
    * ～のではないか is a very common pattern you should be familiar with, and is asked and answered here: [ではないか Grammar translation](https://japanese.stackexchange.com/q/17947/5010)  
Basically it's "Isn't it that ～?", "I wonder ～", or "[I'm/they're/etc] afraid
that ～". Lots of examples
[here](http://eow.alc.co.jp/search?q=%E3%81%AE%E3%81%A7%E3%81%AF%E3%81%AA%E3%81%84%E3%81%8B).

