need help understanding passage :)

[myc]

This is from REA (research and education association) PSAT 2006, pg. 31.
The following passagem written in 1849 Henery David Thoreau discusses his philosophy of governemnt.
"I heartily accept the motto,--" That government is best which governs least", and I should like to see it acted up to more rapidly and systematically. Carried out, it finally amounts to this, which also I believe--"That governemnt is best which governs not at all"; and when men are prepared for it, that will be the kind government which they will have. Government is at best but an expedient; but most governments are usually, and all governments are sometimes, inexpedient. The objections which have been brought against a standing army, and they are many and weighty, and deserve to prevail, may also at last be brought against a standing government. The government itself, which is opnly the mode which people have choosen to execute their will , is equally liable to be abused and perverted before the people can act through of it...."

What does the author mean by "Government is at best but an expedient; but most governments are usually, and all governments are sometimes, inexpedient." an expedient is a resource. inexpedient means unwise... I don't understand what the author is trying to say. Can anyone help me?

One of the question asks" Generally speaking, Thoreau believes that___" The answer is "governments are resistant to change and rarely improve." but where does the passage say that?

Thank you so much!
also do you have any advice on improving reading comprehension for the SAT?

[Tdol]

Governments are at best just a means to an end, but most governements are not fit for that task, and all are unfit at some stage.