First of all, while the Dreyse needle gun was indeed a bolt action rifle, it was still a one-shot weapon - it had a bolt, but no magazine, so every shot had to be reloaded manually. It was a successful breechloaded design that allowed the Prussians to use their rifle swarm tactics, where troops sought cover and fired sitting, hunching or even lying down while muzzle-loaded rifles were hard to reload unless you were standing.

The US had its own breechloading weapon in the Hall M1819 rifle and M1833 carbine, which were decently successful weapons. Other countries also experimented with breechloaders - Norway introduced the Kammerlader 1842, for example. However, breechloaders in general had problems with reliability, gas leakage, problems with breeches bursting or wearing out, less power (due to the gas leakage) and complex designs causing icnrease wear and tear. The Dreyse needle rifles needed their needles replaced regularly, and the rifles needed extensive maintenance after a few months in the field, so the availability after a few moths of campaign was really low.

The reliability issue was why many countries, such as Austria, Britain, France (which would later switch with the Chassepot rifle) and the US chose to go with muzze-loaded rifles during the 1850s and 1860s.

The US, while industrialising quickly, was not at the forefront of industrial know-how in the 1860s - casting steel without hidden imperfection was beyond the US industry in the early 1860s, and iron or mild steel was instead wrought or smithed. Gun metal of the highest quality to forge barrels for rifles was generally imported from Britain and barrel smithing was a high skill profession that took time to learn, which is why it took Springfield and its subcontractors years to get production up to cover the needs of the Union army. As an example, when the Prussians gained the industrial know-how to cast steel barrels for their Dreyse rifles sometime after 1862, they were able to increase production immensly. They produced 600 000 rifles between 1842 and 1866, and 900 000 between 1866 and 1870.

The US was also not at the forefront of military tactics or military technology - in general, the US electorate and politicians were wary of standing armies and were unwilling to levy the taxes and tolls needed to finance a military-industrial complex and a fleet and army capable of taking on a grand power in this era. The US army and navy were very small, and with friendly relations with Britain, there were no substantial threat against the US. The army that existed was capable of winning a war against Mexico and fighting the Native American tribes. This resulted in the Civil War being fought with a lot of old arms, imported weapons and by amateurs led by amateurs before the US could slowly bring its superior industrial complex to produce the arms and other supplies needed and organise its armies and professionalise them enough to crush the rebels.

The US used rifled muskets becuse that was what was available, because such weapons were offered by the Austrians (Lorenz) and British (Enfield), who had surplus weapons to export at a time when the domestic production was inadequate to meet the sudden huge surge in demand for arms with the creation of the until then unseen on the American continent mass armies of the US Civil War. The US did have a breechloader design in the Hall rifle and carbine, but it was discontinued in favour of the more traditional muzzle-loaded Springfield rifle because it was cheaper and more reliable, and up til the Civl War quite enough for the needs of the US armed forces.