Criticisem

'Critisise' is a verb, so the noun 'criticism' would fit to encapsulate your point.

Countries with a population of almost 400 Mmillion populationcombined gathered to discuss how they canould tackle this situation with Israel (10 million population), but no conclusion came out.

Numbers in word form are not capitalized after the numerals. Also, in this case, the noun 'population' would go before the description of their total population, along with the word 'of' to express the relation between the noun and the value associated with it. 'Can' would also be replaced by 'could', since this event took place in the past. Also, what was happening with Israel needs to be specified (this situation, this issue, and others.)

This is ridiciulous.

It cannot be explained why thate USA backs Israel.

'+ed' would be used here, as this is its past tense form. If the present was used, it could be 'One cannot explain'. Also, 'the' would be used before 'USA', as the total phrase is 'the United States of America.' This is not the case for every country, but the United States needs it. (Example: 'It cannot be explained why Morroco backs Israel,' 'It cannot be explained why the Republic of France backs Israel.' If the country includes a description of what it is followed by 'of', it likely needs 'the' placed before it.

These governments should not use the excuse of the USA supporting Israel in every areasubject.

'Government' is a compound word 'govern + ment' to mean 'the body that governs.' Also, the word 'these' would be used, as the governments were previously mentioned. 'Area' is correct, but would sound odd to a native speaker. Also, not a huge issue, but this sentence and the one before it can be combined with a comma, since these are two independent clauses that directly relate to eachother. It makes it more comprehensive since you're using the previous sentence to explain why these countries should not use the excuse of the USA backing Israel to support the nation.

When Isreael invested in tech, engineering and science, Arab nations did not do anything.

Now, governments cannot take any action other than condemning it.

Most of them make use of Palestine for their domestic community.

The possessive would be used here to specify it's their domestic community. Your point is understood here (to me, at least), but it comes off as unnatural. Something like 'most of them make use of Palestine for self-serving propaganda' would be more natural.