Bomb building made easy (and America the not so bright?)

I've always regretted the fireworks ban in Australia:  one week a year of experiments and fun with small fireworks seemed to me worth the public risk of a finger lost here or there.

But in the US, where everything from polyester slacks to fireworks are bigger, it appears that the public can readily buy firework kits which provide in one easy hit all the explosives you need for a deadly bomb:

 Where They May Have Gotten the Materials: Wall Street Journal: "Tamerlan Tsarnaev, the elder brother suspected in the Boston Marathon bombings, bought two large pyrotechnic devices in February from a New Hampshire branch of a national fireworks chain, according to executives at the chain's parent company. William Weimer, a vice president of Phantom Fireworks, said the elder Mr. Tsarnaev on Feb. 6 purchased two "Lock and Load" reloadable mortar kits at the company's Seabrook, N.H. store, just over the border from Massachusetts. Each kit contains a tube and 24 shells, he said. Mr. Tsarnaev paid cash for the kits, which cost $199.99 apiece. It wasn't clear if the powder from these fireworks was used in the bombings. ... One federal law-enforcement official briefed on the probe said the government's working theory was that the powder used in the bombs could have come from high-powered fireworks. The official said there were other possible sources for similar powder and investigators hadn't drawn any firm conclusions."

Before now, didn't sales of things like that to the public strike anyone in the US as dangerous?

While I'm on that theme, and sorry to kick a country while its down and all, but events last week didn't exactly paint America as a country that has a good grip on common sense:

*   why allow a fertilizer plant using famously dangerous chemicals so close to a nursing home and residential area?   (I've heard some commentary in Australia over the last few years praising some American States as having affordable housing because of very relaxed town planning laws.  I think Texas is amongst them.   I'm not sure that this accident can be said to be due to planning decisions, but it's certainly an illustration of the value of planning that keeps industrial plants at a significant distance from residential.)

*   by what insanity is a tightening of background checks from gun shows sales controversial?   Sure, it won't have stopped recent killings, because they show that legal gun owners can be too stupid to realise the danger of keeping guns at home in a house with a disturbed relative.   But seriously, as I have argued elsewhere, can you imagine if in Australia there were gun shows in Western Sydney where anyone could rock up and walk out with a gun without a background check?  We would, rightly, think that insane, as would about 95% of the rest of the world.

*  there was something else, but it will come to me later.